Sharon Redrobe, Bristol Zoo's head of veterinary services holds Polly, an African pancake tortoise, who is recovering after an operation to remove a bladder stone the size of a small egg at Bristol Zoo in Bristol, England. During the hour-long operation vets had to cut away a hole in the bottom of Polly's shell in order to remove the bladder stone, which may otherwise have killed her within weeks or months. The bladder stone weighed 19g and measured 1.5 inches by 1.2 inches. Polly measures 5.5 inches long from head to tail.

Sharon Redrobe, Bristol Zoo's head of veterinary services holds Polly, an African pancake tortoise, who is recovering after an operation to remove a bladder stone the size of a small egg at Bristol Zoo in Bristol, England. During the hour-long operation vets had to cut away a hole in the bottom of Polly's shell in order to remove the bladder stone, which may otherwise have killed her within weeks or months. The bladder stone weighed 19g and measured 1.5 inches by 1.2 inches. Polly measures 5.5 inches long from head to tail. (Getty photo by Matt Cardy)